I love the shading you have on the tree. It's got a great sense of lighting and color that I think gives it a great environment. Also there's some subtle perspective changes in each of the levels of the tree that just makes it look great. One problem that I see is that it's mirrored, which means the light is coming from the top-down. You should give more thought to the environment where the tree is placed (a Christmas tree outside?), and where the light is coming from. The only location for a Christmas tree I can imagine the lighting coming from directly above is a streetlight. So think about where you
really want the tree to live, and then give it a suitable light source. (I hope you keep those colors, though. They're great).
Also, Aelyrin's right in that a real Christmas tree doesn't work like that. Usually it's a lot thinner (meaning it's easier to see the trunk), and less like fur. The branches are perfectly straight, and they actually stick up (unless you have some pretty heavy ornaments).
This calls for a
reference photo!